Forestry machines, such as harvesters or feller bunchers, are typically used for industrial scale logging. A feller buncher can quickly cut and bunch a number of trees together before felling them. The feller buncher then places the bunched trees in a pile for a skidder, forwarder, or other means of transport for further processing.
Typical feller bunchers may include a tracked or a wheeled chassis, an engine, an operator cab, a grabbing device, and a cutting tool. The grabbing device may be attached to an extended moveable arm. The cutting tool may be a chain-saw, circular saw or shears. The grabbing device and cutting tool may be part of a single device, such as a felling head or harvester head. While the grabbing device holds onto a tree, the cutting tool severs the tree at its stump. The feller-buncher may cut and bunch more than one tree together before lowering the trees in a horizontal position onto the ground or a bundle pile.
When operating a feller-buncher, an operator of the machine may run different speeds for different functions. For example, the operator may run the machine at one speed while cutting trees and may run at another speed while tracking to and from the bundle pile. At a same time, the operator has to handle numerous other controls during operation and may need to travel long distances, which may result in the operator experiencing difficulty due to fatigue, challenging work environments, and/or the operator's limited skill level. Therefore, there is a need for speed control systems and methods that help minimize operator input for speed control, thereby enabling convenient overall operation of the machine.
For example, U.S. Pat. No. 8,364,356, entitled, “Drive Control System for a Vehicle and Method,” describes a system and method for track adjustment. The system of the '356 patent provides a tracking adjustment mode for adjusting the straight line travelling of a vehicle. In the '356 patent, a left joystick is linked to a hydraulic motor that controls the left side wheels of the machine, while a right joystick is linked to a hydraulic motor that controls the right side wheels of the machine. A user of the system of the '356 patent can then initialize the tracking adjustment mode to make relatively small changes to the output of the hydraulic pump and/or the hydraulic motors so that the machine travels straight when the joysticks are positioned in the positive center position.